System to reduce sediment toxicity

ABSTRACT

A method and apparatus for the treatment of sediment. The apparatus provides a plurality of injection sites for injecting a biochemical oxidant into the sediment. The oxidant is useful for oxidizing a bacterial growth inhibitor to a non-inhibiting form thus permitting bacterial growth and thus greater numbers for sediment detoxification.

This application is a continuation-in-part of U.S. Ser. No. 08/084,620filed Jul. 1, 1993, now abandoned.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for thetreatment of sediment and more particularly to a chemical treatmentmethod and apparatus to effect such treatment.

BACKGROUND OF THE INVENTION

Generally speaking, most of the biodegradation studies and treatmentsare done in reactors (Jafvert and Rogers 1991). The largest reactor is aDutch system where a mobile aerator moves along the treatment pond tomaintain oxic conditions (Van Veen and Annokkee 1991). Other largetreatments include landfarming (Van Dillen 1991) and the excavation andconstruction of a hill of contaminated soil with drainage tiles,nutrient dosing and sprinkler systems (Litchfield et al. 1992). Thesesystems all require that the sediment be dredged and processed in siteswhich can involve the potential problems of security, cost, and publicacceptance.

Some soil reclamation using biodegradation has occurred withoutexcavation. The success of these treatments has varied greatly (Lee etal. 1988). Some contaminants cannot be readily biodegraded. Sometreatments may not have provided the right environmental conditions forthe microbes to completely biodegrade the organic wastes. Most of thefailed bioremediation treatments in groundwater are related to eitherpoor access to the wastes or to the blockage of the aquifer by theenhanced growth of microbes. The latter two problems do not apply tolake sediment on a macroscale; however, all sites can contain somepolynuclear aromatic hydrocarbons (PAHs) locked in microsites which aretherefore not biodegradable (Van Dillen 1991). Presumably theserefractory PAHs would not be toxic. In similar studies it was found thatcoal dust contains PAHs but relative to coal tar and creosote, it isbiologically inert (Alden and Butt 1987).

Bioremediation of groundwater and soils is a growing industry. As longas the treatment is preceded by an analysis of the treatability andtoxicity of the site, it is a promising remedial option. Some toxinscannot be treated by biodegradation, but the cost of assessment isjustifiable in that a detailed preassessment is substantially lessexpensive than excavation and chemical or physical treatment.

Bubbling the water column with oxygen has been proposed as a method ofoxygenating the sediment (Murphy 1990). Some lake aeration treatments inGermany successfully oxygenated sediments but treatment with pure oxygenof some lakes in Switzerland did not oxygenate sediments (Gachter 1987).The engineering techniques are not completely developed, the treatmenttime may be long, and recovery difficult to predict accurately.

Further prior methods for treating sediment of sludge include the methodof decontaminating wastewater sludge taught by Nicholson in U.S. Pat.No. 4,781,842. Reference is made to the use of lime, cement kiln dustand lime kiln dust for treating biological sludge. The goal of thetreatment is to fertilize agricultural land. The reference does notaddress the problem of treating sludge associated with a water body forthe purpose of enhancing natural microbiological degradation.

U.S. Pat. No. 5,008,020, discloses the use of a metal carbonate and ametal bicarbonate for solidifying waste material into a granularparticulate form. The patentees do not discuss the merits of oxidationbiodegradation inhibitors in order to effect more efficientbiodegradation.

Conover, in U.S. Pat. No. 5,039,427, teaches a method for removingsuspended solids and to precipitate and inactivate phosphorus in lakewater by adding aluminum hydroxide sulphate. The reference does notdiscuss oxidation of sulphide to sulphate to reduce inhibition ofnatural microbial biodegradation.

U.S. Pat. No. 4,877,524, teaches an apparatus for treating bodies ofwater for correcting chemical, biological or other imbalances. Thereference primarily relates to dispensing a treatment agent within awater body, the dispensing rate being proportional to the boat speed.Both aluminum sulphate and sodium aluminate are taught as treatmentmaterial among others. There is no provision in the apparatus forinjecting or otherwise contacting the sediment with biochemical oxidantand accordingly, no contemplation for enhancing the natural microbialdegradation of the sediment and more particularly the toxins of thesediment.

A further apparatus which is known in the art and which is directed toan apparatus for spraying plants is taught in U.S. Pat. No. 1,348,038,issued Jul. 27, 1920 to Neumeyer. When the disclosure of the Neumeyerreference is fully considered, it is clear that the apparatus in no waywas intended for use within a thick and often viscous material such assediment. Neumeyer's arrangement provides branched pipes which arearcuated shaped and include a nozzle, however, it is clear that they areconnected to a main branch pipe by a fitting. Further, the terminal endof the branch pipe is connected to a fitting and subsequently to a mainsupport beam. According to the Neumeyer apparatus, it would appear thatthe arcuate pipes are fixedly secured to the overall apparatus at twodistinct points and, accordingly, it would appear that flexibility suchas would be required when the apparatus encountered branches, trunks oftrees, thick sediment rocks etc., would not be possible.

The Neumeyer arrangement further provides shares or lifting deviceswhich travel in valleys between the crests of soil. Accordingly, it isclear that the apparatus is adapted for use on a surface which has apreformed trough within which the shares or lifting devices can travel.The shares are designed to travel on the ground and maintain the pointsof the shares either on or slightly above the surface of the ground andin position to engage under fallen or trampled portion of vines.Furtherstill, the Neumeyer disclosure indicates that lifting members aredesigned so that they do not dig into the ground but will underridevines and lift them to an appropriate height.

As a further limitation in the Neumeyer reference, the system isdesigned such that the fluid transportation members are the same memberswhich would experience the force realized when debris, thick sludge orsediment etc. is encountered. It would be more desirable to have aseparate support system for digging into the soil, which support systemwould support a separate means of transmitting a treatment fluid intothe sediment.

Shuck et al. in U.S. Pat. No. 4,268,398, teach a method for rendering asludge deposit in a waste water treatment facility into a pumpablemixture for relocation. This reference does not discuss an in-situprocedure for natural biodegradation of the sludge.

Further generally related references include U.S. Pat. No. 5,055,204 andCanadian Patent Application Nos. 2,007,455 and 2,016,310.

In view of the prior art, there exists a need for a sludge treatmentprocess capable of being performed in-situ without stirring up thesediment into the water column and which permits a relatively large areato be treated quickly.

SUMMARY OF THE INVENTION

One object of the present invention is to provide an improved method fortreating sludge and an improved apparatus for effecting the method.

In accordance with another object of one embodiment of the presentinvention, there is provided, a method of effecting natural microbialbiodegradation of polynuclear aromatic hydrocarbons and petroleumhydrocarbons in sediment containing microbes and polynuclear aromatichydrocarbons, and petroleum hydrocarbons comprising the steps of:providing a biochemical oxidant for detoxifying a microbial toxinproduced during microbial biodegradation of the polynuclear aromatichydrocarbons and petroleum hydrocarbons; contacting the sediment withthe oxidant to detoxify the toxin; and effecting microbialbiodegradation of the polynuclear aromatic hydrocarbons and petroleumhydrocarbons.

The process of microbial decay results in the production of hydrogensulphide. The presence of this compound generally impedes thebiodegradation of the compound. The addition of a biochemical oxidante.g. a bivalent alkaline earth chloride or nitrate or monovalent nitratehave been found useful.

In accordance with another object of the present invention, there isprovided a method of effecting natural microbial biodegradation ofpolynuclear aromatic hydrocarbons and petroleum hydrocarbons in sedimentcontaining the polynuclear aromatic hydrocarbons and petroleumhydrocarbons and microbes, comprising the steps of:

contacting the sediment in a first contacting step with the oxidant at afirst level therein;

contacting the sediment in a second contacting step with the oxidant atleast at a second level in the sediment, the second level beingdifferent from the first level; and

effecting the natural microbial biodegradation of the polynucleararomatic hydrocarbons and petroleum hydrocarbons.

By oxidation of the inhibitor, substantial success was realized in thereduction of toxins in the sediment. The successful results werecompounded by the fact that the sediment was contacted at a plurality oflocations.

The overall process is continuous such that the treatment of the sludgecan be effected quickly over a large area.

Nutrients may be added with oxidant concurrently or conterminously.Further, the addition of emulsifier surfactants, or other suitabletreatment aids may be employed. Depending on the specific sitevariables, a pretreatment may be desirable in order to increase theefficiency of the procedure.

Apparatus suitable for facilitating maximum exposure of the oxidant tothe sediment includes a dispensing arrangement therefor for dispensingthe oxidant into the sediment in at least two locations simultaneously.

An apparatus for treating sediment in a water body, said sedimentcontaining chemical pollutants, comprising:

a main support member;

a first dispensing means mounted in spaced relation to said main supportmember adapted for dispensing a treatment compound into said sediment tobe treated at a first level;

a second dispensing means adapted for dispensing treatment compound intosaid sediment at a second level, said second dispensing means comprisinga plurality of individual flexible hoses, each having a nozzle at oneend and connected at an opposed end to said first dispensing means forreception of said treatment compound;

resilient support means for supporting a nozzle and hose of said seconddispensing means, said resilient support means for penetrating saidsediment, said resilient support means comprising a plurality offlexible fingers mounted to said main support member and separate fromsaid first dispensing means and said second dispensing means; and

means for connection for said first dispensing means with a supply ofsaid treatment compound.

A still further object of the present invention is to provide anapparatus for treating sediment in a water body, said sedimentcontaining chemical pollutants, comprising, in combination:

a main support member;

a first dispensing means mounted in spaced relation to said main supportmember, said first dispensing means for dispensing a treatment compoundinto said sediment to be treated at a first level;

a second dispensing means adapted for dispensing said treatment compoundinto said sediment at a second level, said second level dispensing meanscomprising a plurality of individual flexible hoses, each having anozzle at one end and connected at an opposed end to said firstdispensing means;

said first dispensing means having means for connection with a supply ofsaid treatment compound;

resilient support means for supporting said second dispensing means andfor penetrating said sediment, said resilient means comprising aplurality of arcuately-shaped flexible fingers mounted to said mainsupport member and separate from said first dispensing means and saidsecond dispensing means;

mounting means for mounting said apparatus to a carrier vessel; and

a carrier vessel for mounting said mounting means.

Having thus generally described the invention, reference will now bemade to the accompanying drawings illustrating preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of the apparatus of thepresent invention;

FIG. 2 is an enlarged perspective view of one embodiment of the sedimenttreatment apparatus;

FIG. 3 is a cross-section of FIG. 2;

FIG. 4 is an enlarged view of the mounting and fluid distribution forthe sediment treatment apparatus;

FIG. 4A is a plan view of the sediment treatment apparatus support;

FIG. 4B is a schematic illustration of the apparatus in use;

FIG. 5 is a series of graphs illustrating the concentrations of variouscontaminants;

FIG. 6 is a schematic illustration of the test area;

FIG. 7 is a graphic illustration of the redox potential of St. MarysRiver sediment cores;

FIG. 8 is a histogram illustrating the effect of ferric chloride onsediment hydrogen sulphide for the St. Marys River treatment;

FIG. 9 is a histogram illustrating the ATP-TOX results from Sault Ste.Marie for the first ferric chloride sediment injection;

FIG. 10 is a series of histograms illustrating the sediment toxicity ofphotobacterium phosphoreum bioassay for data gathered at St. MarysRiver;

FIG. 11 is a histogram illustrating the Daphnia magna bioassay resultsillustrating the average percent survival;

FIG. 12 is a graph illustrating the percent mortality for theDMSO/methanol sediment extract;

FIG. 13 is a histogram illustrating the average percent survival forDaphnia magna bioassay results for the Hamilton Harbour Stelco Hotspotsite #1;

FIG. 14 is a histogram illustrating the average percent survival forDaphnia magna bioassay results for the Hamilton Harbour Stelco Hotspotsite #2;

FIG. 15 is a histogram illustrating the average percent survival forDaphnia magna bioassay results for the Hamilton Harbour Stelco Hotspotsite #3;

FIG. 16 is a histogram illustrating the results of FIGS. 13, 14 and 15;

FIG. 17 is an illustration of the toxicity severity of Hamilton Harbour;

FIG. 18 is an illustration of the toxicity of Hamilton Harbour sedimentsfor photobacterium;

FIG. 19 is an illustration of the Hamilton Harbour sediment injectionsite;

FIG. 20 illustrates data generated in denitrification experiments forbottle incubations;

FIG. 21 illustrates data generated in denitrification experiments for250 ml bottle incubations;

FIG. 22 illustrates data generated in denitrification experiments for 2L bottle incubations;

FIG. 23 illustrates data generated in denitrification experiments for250 ml bottle incubations;

FIG. 24 illustrates data generated in denitrification experiments for 2L bottle incubations;

FIG. 25 illustrates the biodegradation of the sixteen priority pollutantpolynuclear aromatic hydrocarbons;

FIG. 26 illustrates the denitrification data comparing Hamilton HarbourDeep Basin, Stelco Hotspot and St. Marys River;

FIG. 27 illustrates the effect of the nitrate treatment on thePhotobacterium;

FIG. 28 illustrates headspace GC/MS analysis for a variety of organiccompounds for a control before treatment and for data gathered afternitrate treatment; and

FIG. 29 illustrates the biodegradation of volatile toxins in the Dofascoboatslip before and after treatment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to the apparatus aspect of the present invention,FIG. 1 illustrates a first embodiment of the present invention, inperspective, as situated on a carrier vessel.

Generally, the apparatus includes movable lifting apparatus 10 having amain support platform 12 rotatably mounted to the carrier vessel 14 forrotation relative thereto, the rotation being achieved by making use ofconventional gear arrangements (not shown) or other suitable means. Loadbearing masts 16, 18 are connected to the platform 12. A winch cablesystem 20 includes winches 22 extends over pulleys 24 provided on theload bearing masts 16 and 18. One of the winch cables of the cablesystem 20 includes a connecting member 26 suitable for connection withthe sediment treatment apparatus, generally denoted by numeral 30. Asupport system is provided for supporting and assisting in thepositioning of the treatment apparatus 30, and will be discussedhereinafter.

In one embodiment of the treatment apparatus, best illustrated in FIG. 2and 3, an elongate hollow spray bar 32 is included having opposed ends34 (FIG. 1) and 36. The spray bar 32 includes a plurality of nozzles 38distributed along the length of bar 32 in a spaced and aligned relation.The nozzles 38 are inclined downwardly relative to a horizontal plane. Asecond set of nozzles 40 are distributed along the length of spray bar32 in spaced and aligned relation radially spaced from nozzles 38. Bothnozzles 38 and 40 are in fluid communication with spray bar 32.

As is illustrated in the example, the sediment treatment apparatus 30 iscomposed of a plurality of connected and similar units and accordinglythe description will be limited to one such unit.

Spaced above spray bar 32 there is provided a mounting member 42comprising a metal tube having opposed ends 44 (FIG. 1) and 46. Aplurality of such members 42 are connected in end-to-end relation bysuitable fasteners as illustrated. Each remote or terminal end as wellas the end connection between mounting members 42 includes a spacermember 48, which not only spaces the members 42 from the spray bar 32,but additionally serves to impart support to the spray bar 32.Connection of spacer members 48 to member 42 and bar 32 is achieved bysuitable fasteners, welding etc.

Each mounting member 42 includes a plurality of arcuate fingers 50 eachconnected thereto at a single point by bolts 52. The fingers 50 arearranged in longitudinally aligned and spaced relation. Each finger 50subscribes to a generally sinusoidal configuration and each comprises arigid metal suitably bent into the indicated shape. The shape of eachfinger 50 permits resilient flexibility. A free end 54 of each finger 50is laterally and vertically spaced from the spray bar 32.

Each finger 50 includes, spaced from free end 54 thereof, a nozzlemounting 56 for mounting a nozzle 58. A conduit 60 extends between andconnects nozzle 58 with nozzle 40 such that fluid communication isestablished. In the arrangement, therefor, finger 50 remains separatefrom each conduit 60 and nozzle 58 thus affording flexibility andpenetration into the sediment without any difficulty in dispensingfluid.

Treatment fluid is distributed to each spray bar 32 by a distributionconduit 62 connected to each spray bar 32 inwardly of the end thereof bya swivel type connector 64 well known to those skilled. This isgenerally illustrated in FIG. 4. Each conduit 62 terminates for fluidconnection with a main feeder conduit 66 (FIG. 1). Conduit 66 isconnected to a fluid treatment supply drum 68 centrally located on thecarrier vessel to act as ballast. A pump (not shown) may be positionedintermediate of supply drum 68 and feeder conduit 66 or the fluid may bedistributed by negative pressure.

Treatment fluid travelling through each spray bar 32 will be dispensedthrough nozzles 38 as well as through nozzles 40, all conduits being influid communication.

At least the spray bars 32 adjacent the terminal sections thereoffurther include frame mounts 70 for releasably coupling the treatmentapparatus 30 to a frame 72.

FIG. 4 illustrates an enlarged view of the attachment of the end offrame member 74 to spray bar 32 (removed for clarity) as is generallyillustrated in FIG. 1. Fastener 76 links a flange 78 on member 74 toframe mount 70. The frame 72 may include a plurality of members 74 whichconverge, and the member thereof will vary depending on the size of thetreatment apparatus. The frame 72 permits easy manipulation of theapparatus from a submerged position to a storage position, the latterposition being illustrated. Frame 72 includes a connection site 80 forconnection with connecting member 26 on winch cable 20.

FIG. 4A illustrates the hangar assembly 90 for positioning the assembly30 into the sediment at the desired position.

The assembly 90 includes a main load bearing member 92 which terminatesat a horizontally disposed bracket 94 for connection with spray bar 32(not shown). Connection to spray bar 32 may be by any suitable means,e.g. clamps, bolts etc.

Bracket 94 and member 92 are further reinforced by braces 96 extendingtherebetween.

In order to permit treatment of sediment in a variety of situationswhere the depth requirement varies, load bearing member 92 may include aplurality of telescopic sections of tube 98 or may be extended byprogressive manual connection of further lengths of tubing sections 98.

Load bearing member 92 may be pivotally connected to the load bearingmasts 16 and 18, described herein previously, or may be connecteddirectly to platform 12 for easy manipulations of member 92. Thespecific mounting position of member 92 will depend upon the specificparameters in the treatment area, e.g. water depth etc.

Generally, the tubing sections 98 may comprise rigid aluminum materialor other suitable corrosion resistant materials. This material provisionis additionally applicable to the overall assembly 90 and frame 72.

In operation, the treatment apparatus 30 is moved from the storageposition shown in FIG. 1 to one possible use position shown in FIG. 4Bwhere the apparatus is submerged below the surface of the water, W, tocontact the sediment bed, S. The disposition of the apparatus relativeto the sediment S, will vary depending on the condition of the sediment,current conditions, etc.

In the position shown, both the spray bars 32 and the fingers 50 contactthe sediment, S, as illustrated. The fingers 50 permit deeperpenetration of the nozzles 58 and more specifically the treatmentmaterial dispensed therethrough, into contact with the sediment. Thenozzles 38 dispense the treatment material in a second position spacedfrom that of the treatment supplied by nozzles 58. This two-pointinjection system has a dramatic effect on the sediment detoxification aswell be evinced by the data discussed hereinafter.

The treatment apparatus 30 is dragged along the sediment bed as thecarrier vessel travels the area to be treated. The arcuate fingers 50are particularly advantageous for the sediment treatment since the sameare resilient and basically unaffected by irregular bed topography,small debris etc. When encountered, the fingers 50 simply flex andreturn to a normal disposition as the apparatus continues to be advancedalong the sediment bed. Recovery of the apparatus from the sediment maybe achieved with the winch system described previously.

In preferred form, the overall length of the apparatus is eight (8)meters with the spacing between nozzles 38 and 58 being between 10 andabout 20 centimeters. Such spacing permits uniform dispersion within thesediment as opposed to localized areas of treatment.

The rate at which the treatment fluid is injected into the sediment maybe timed with the carrier vessel speed i.e. a higher vessel speed willrequire a higher rate of injection of fluid into the sediment. In analternate embodiment, the treatment apparatus 30 and the ancillaryequipment (winch, a bearing mast etc.) as well as the submergingprocedure may be effected by robotics controlled from the shore or at apoint distant from the treatment area. This arrangement would reduce theexposure of human workers to the hazardous sediment material andpresence around the heavy equipment.

The use of monitoring means e.g. sonar equipment, cameras ultrasonicequipment etc. are all envisioned for use with the apparatus in order tomonitor gross sediment topography irregularities or obstacles with whichthe apparatus 30 cannot contend.

Still further, the connection points between spray bars 32 and betweenmounting members 42 may be hinged to permit folding of the apparatus 30.In addition, the apparatus may be telescopic.

The examples illustrated teach a two-point treatment injection systemand it will be clearly understood that a multiplicity of injectionpoints may be provided simply by, for example, the addition of a furtherseries of fingers having a greater length than the previous series.

Having thus described the apparatus, reference will now be made to theexperimental procedures and generated data.

GENERAL EXAMPLE 1--FERRIC CHLORIDE INJECTION

Earlier laboratory trials with Hamilton Harbour sediments indicated thatthe addition of iron reduced toxicity to Photobacterium phosphoreum,Daphnia magna, Salmo gairdneri, Pimephales promelas, and Hexagenialimbata. The seasonal change in sediment toxicity also seemed related toa change in redox, albeit the relationship was not firmly established.Also there was a correlation between the toxicity of the sediments toDaphnia magna and the chemical oxygen demand of the sediments. The mostappropriate hypothesis to explain these observations is that much of theacute toxicity of the sediments of Hamilton Harbour was caused byreduced chemicals, probably hydrogen sulphide.

Hydrogen sulphide is very toxic. The LC₅₀ for various species are:Assellus 1.07 mg/L, Crangonyx 0.84 mg/L, Gammarus 0.059 mg/L, Baetis0.020 mg/L, Ephemera 0.361 mg/L, and Hexagenia 0.111 mg/L. Chronicanalysis indicates that no-effect levels are about 10% of the LC₅₀(Oseid and Smith 1974). Although hydrogen sulphide toxicity is wellknown, few studies report it in sediments. US EPA (1986) describehydrogen sulphide as "ephemeral" which indicates that infrequentsampling would not measure hydrogen sulphide. Another limitation is thatsome professional laboratories use procedures too insensitive to detecttoxic concentrations of hydrogen sulphide.

Studies with ³⁵ S-radiolabels have measured the geochemical reactions ofsediment sulphur well. For example, Nedwell (1980) determined sulphatereduction in summer is 50-100 times faster than in winter. Withintensive monitoring, Ripl (1986) observed large seasonal changes insulphate; if only a few percent of the seasonal change in sulphate wereconverted to hydrogen sulphide, the sediments were very toxic. Thissimplistic assumption may underscore the ecological importance ofseasonal changes in hydrogen sulphide toxicity. Ingvorsen and Jorgensen(1982) observed a 20-fold seasonal change in sulphate reduction, but itwas matched by seasonal changes in hydrogen sulphide flux from thesediments of 10³ -10⁴ fold! At low rates of hydrogen sulphideproduction, it was mostly adsorbed to particles, but at high rates ofhydrogen sulphide production, the binding sites were saturated and thepulsed release of hydrogen sulphide would have killed many benthicorganisms.

Similar sulphur geochemical cycling and sediment toxicity must occur inthe hotspots of the Great Lakes but it is not documented. Decades ago,all steel mills discharged large quantities of sulphur from severalsources such as sulphur balls from the coking process or spent sulphuricacid in pickling liquor. The areas in Hamilton Harbour and the St. MarysRiver where these wastes would settle are anoxic and hydrogen sulphideshould form.

Inadequate documentation of the sulphur biochemistry could lead tomisinterpretation. Hydrogen sulphide has a half life of about 19±19 h(Table 16 in Zehnder and Zinder 1980). Thus it is easy to lose thetoxicity by sample handling, such as is commonly done when bubblinginvertebrate bioassays with air. The reported absence of Hexagenia fromthe St. Marys River has been explained by correlation analysis toreflect oil and grease toxicity (St. Marys RAP 1992), but it couldeasily be caused by hydrogen sulphide toxicity.

Samples were collected on several trips to St. Marys River and severaltrips to Hamilton Harbour with Ponar (Sault) or Shipek (Hamilton) grabsamplers, TechOps corers, and sediment traps. The sediment traps weredeployed a meter about the sediments to determine if the sedimentinjection equipment resuspended sediments. In the St. Marys River, fourtraps were set at one upstream site and four traps were set at one sitedownstream of the treatment area.

All St. Marys River samples were stored in a cold room at the GreatLakes Forestry Research Centre, and processed for shipping on ice, i.e.,cores were extruded there at 1 cm intervals. The Eh and pH of sampleswere recorded at the site. All Hamilton Harbour samples were broughtback to the institute within hours of sample collection. All sampleswere chilled and processed quickly, i.e., all bioassays were processedwithin days of sample collection. Sediment samples were subsampled; halfwas freeze dried for metal analysis and half was frozen and retained fororganic analysis.

The ATP-TOX method of Xu and Dutka (1987) was used on 10% DSMO 10%methanol elutriates. Equal volumes of sediment and DMSO were mixedtogether and shaken vigorously by hand for 2 minutes. The homogenizedslurry was then centrifuged for 20 minutes at 10000 rpm. This systemuses the measurement of ATP as indication of microbial growth. If whencompared to a control, a sample inhibits ATP production (i.e., growth),a toxic effect is assumed.

Daphnia magna bioassays were done on aqueous elutriates. Within twoweeks of collection all samples were extracted with equal volumes ofdistilled water on an end-over-end shaker for 16 h. After extraction,sediment extracts were centrifuged for 20 min at 1000 g. Elutriates werecentrifuged, not filtered. Filtration can remove colloidal material thatwould not settle from disrupted sediment and that may contain toxicmetallic or organic contaminants. Ten Daphnia less than 24 h old wereintroduced to 25 mL of test medium and placed in a 25° C. incubator for48 h. A 16 h light and 8 h dark photoperiod was used. Prior to allexperiments, pH and dissolved oxygen were measured and if the oxygenconcentration was less than 8 mg/L, the sediment extracts were bubbledwith purified air for 16 h. If more than 10% of the control Daphnia diedwithin 48 h, the experiment was repeated.

Photobacterium bioassays were run on whole sediments (Brouwer et al.1990). Dilutions for LC₅₀ analysis were done with clean sediments froman organic rich sediment from a marsh near Long Point, Lake Erie.

SEDIMENTS AT THE BELLEVUE PARK SITE, ST. MARYS RIVER

Unlike Hamilton Harbour, metals (FIG. 5) and the 16 priority pollutantpolynuclear aromatic hydrocarbons (PAHs, Table 1) are comparativelydilute at the Bellevue Park test site in the St. Marys River (FIG. 6).However, sediment samples from near Bellevue Park have highconcentrations of oil and grease (1.4%, 1.6% and 2.4%) and wood fibres.

                  TABLE 1                                                         ______________________________________                                        PAH Concentrations in Surficial Sediment                                      of Bellevue Marine Park Area                                                                  Sample Range                                                                  (ng/g)                                                        ______________________________________                                        Naphthalene       3137-6878                                                   Acenaphthylene    152-318                                                     Acenaphthalene    169-360                                                     Fluorene          356-540                                                     Anthracene        1913-3425                                                   Phenanthrene       478-1227                                                   Fluoranthene      2599-6831                                                   Pyrene            2021-5485                                                   Chrysene          1068-3269                                                   Benzo(a)anthrancene                                                                             1353-3680                                                   Benzo(b)fluoranthene                                                                            2004-2223                                                   Benzo(k)fluoranthene                                                                            1512-2202                                                   Benzo(a)pyrene     964-3114                                                   Dibenzo(a,h)anthracene                                                                           275-1040                                                   Indeno(1,2,3-cd)pyrene                                                                          130-411                                                     Benzo(g,h,i)perylene                                                                             370-1214                                                   Total PAHs        16989-42019                                                 ______________________________________                                    

A high concentration of a complex PAH (retene, 2 μg/g) was found in theSt. Marys River sediments. Retene can occur naturally from degradationof conifers but it can also be associated with pulp and papermanufacturing. The concentrations of many of the priority pollutantchlorinated organic compounds is near or at background levels (Tables 2and 3).

Decay of the wood fibre and other wastes results in a reducingenvironment as indicated by the black colour, high ammonia (1.5-2.3mg/L), and low redox (FIG. 7). Note that the deeper sediments are moreoxic. This observation reflects the relatively recent discharge oflabile organic wastes over older more oxic sediments. Also note that theredox of the sediments changes seasonally. By November the surfacesediments have become oxygenated (FIG. 7). It is a fortunate situationin that oxidation treatment of the surface sediments could not becompromised by diffusion of reduced materials such as hydrogen sulphidefrom deeper sediments. Also the required depth of treatment is only 15cm.

The highest observed concentration of hydrogen sulphide in the sedimentwas in June (FIG. 8). By the end of August most of the hydrogen sulphidehad been oxidized. The sediment treatment with ferric chloride greatlyreduced the concentration of hydrogen sulphide.

The ATP-TOX bioassay indicated a seasonal change in toxicity (FIG. 9)that closely matched that of the hydrogen sulphide concentration. Also,the ferric chloride treatment reduced the toxicity of the ATP-TOXbioassays in tandem with the hydrogen sulphide complexation.Photobacterium phosphoreum bioassays also indicated a seasonal change intoxicity but they were not done as intensively as the ATP-TOX bioassays(FIG. 10). Daphnia magna bioassays with aqueous extracts indicated notoxicity (FIG. 11 but some DMSO extracts with Daphnia could measuretoxicity (FIG. 12).

                  TABLE 2                                                         ______________________________________                                        PCB Concentrations in Surficial Sediment                                      of Bellevue Marine Park Area                                                                    Sample Range                                                                  (ng/g)                                                      ______________________________________                                        PCB 18              ND-0.66                                                   PCB 52              ND-5.13                                                   PCB 49              ND-5.43                                                   PCB 44              ND-3.69                                                   PCB 101             2.48-5.77                                                 PCB 151             ND-9.23                                                   PCB 118 + 149       2.29-15.57                                                PCB 105             ND-1.92                                                   PCB 138             2.91-6.36                                                 PCB 183             ND-2.94                                                   PCB 194             ND-0.85                                                   Total PCB           80.43-299.28                                              ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        Organic Contaminant Concentrations in Surficial Sediment                      Of Bellevue Marine Park Area                                                         Sample Range          Sample Range                                            (ng/g)                (ng/g)                                           ______________________________________                                        1,3 DCB  ND          Aldrin      ND                                           1,4 DCB  ND          OCS         ND                                           1,2 DCB  ND          g Chlordane ND                                           HCE      ND          o,p DDE     ND                                           1,3,5 TCB                                                                              ND          a Endosulfan                                                                              ND                                           1,2,4 TCB                                                                              ND          a Chlordane ND                                           1,2,3 TCB                                                                              ND          t Nonachlor ND                                           1,2,3,5 TECB                                                                           ND          Dieldrin    ND                                           1,2,4,5 TECB                                                                           ND          p,p' DDE    1.97-3.17                                    1,2,3,4 TECB                                                                           ND          o,p' DDD    ND                                           PECB     ND          Endrin      ND                                           2,3,4,6 TECB                                                                           ND          B Endosulfan                                                                              ND                                           A BHC    1.66-4.14   p,p' DDD    1.22-3.32                                    HCB      ND          o,p' DDD    ND                                           PECA     ND          Methoxychlor                                                                              ND                                           Lindane  ND          Mirex       ND                                           Heptachlor                                                                             ND                                                                   ______________________________________                                    

Two other bioassays indicated little or no toxicity. Dilution bioassayswith Hexagenia (mayfly nymphs) from four field trips in 1991 (February,June, July, and August) indicated no toxicity. Bioassays with Lactucasativa (lettuce) detected little toxicity. These latter bioassays arenot sensitive to hydrogen sulphide toxicity.

The bioassay results were not as clear as visual inspection of the sitewas. Very few benthic invertebrates were seen; the sediments werevirtually sterile to organisms. The main acute toxin is hydrogensulphide and some laboratory bioassays cannot detect this toxin.

Three sets of Daphnia toxicity dilution experiments in Hamilton Harbouralso observed a seasonal change in sediment toxicity (FIGS. 13, 14 and15). Some variation exists and the trends are more obvious by looking atthe average toxicity (FIG. 16). In winter, these sediments have littletoxicity. However, if these winter samples are purged with nitrogen,then sealed for a month to go anoxic, then bubbled with air for 2-3 h tooxygenate them, they are highly toxic. This length of oxygenationprovides oxygen saturation but it is less than the half life of hydrogensulphide oxidation (19 h).

By late fall, the sediment samples from the Stelco Hotspot were stillhighly toxic. These observations differ from the St. Marys Riversediments where hydrogen sulphide toxicity was almost gone by lateAugust. The differences in extremes of hydrogen sulphide concentrationssupport the hypothesis that the Stelco Hotspot with 100 mg/L of hydrogensulphide will stay toxic for much longer than the St. Marys Riversediments with 4 mg/L hydrogen sulphide.

New toxicity maps with Daphnia magna (FIG. 17) and Photobacteriumphosphoreum (FIG. 18) indicate much less toxicity than earlier maps(Brouwer et al. 1990). The new maps are done from analyses of surfacesediment (0-1 cm), whereas the old maps were done from analyses of Ekmandredge samples (0-15 cm). In part, the surface sediments have lesscontaminants, but the deeper sediments have less access to oxygen andanoxic decay produces hydrogen sulphide.

If the acute toxicity is controlled by hydrogen sulphide, then nobiodegradation occurs in the deeper sediments and some occurs at asuppressed rate in the most recent sediments. The proof of this lasthypothesis is found in the PAH data. The surface sediments have muchless naphthalene than the deeper sediments (Tables 4 and 5). Naphthaleneis biodegradable (Murphy et al. 1992). Some recovery from source controlis occurring, but it is slow. The rate of recovery is uncertain in thedeep basin. The deeper sediments of the Stelco Hotspot, i.e., >2 cm deepare not recovering and will likely remain uninhabitable to benthos fordecades.

Two sediment injection trials were conducted in the St. Marys River nearBellevue Park. The first trial was relatively successful butmodifications were made to improve efficiency before the secondinjection trial. The system, described herein previously, for injectingiron into sediments was built and tested for the first time in the St.Marys River on Jul. 10, 1991. The system had the capacity to treat alarge area; three 45-gallon barrels of ferric chloride were injected inless than an hour over an area 90 m by 12 m. The equipment was tough inthat it survived bouncing over logs and other debris. In spite of minorengineering problems, the equipment worked well. The colour of the ironin the sediment cores indicated that the top 9 cm of sediments weretreated. Refinements in the pumping equipment were needed before largerareas could be treated. The chemical pump required an air compressor andonly large ones were available from rental agencies. A compact Honda aircompressor was bought to provide more free deck space. The pore size ofthe nozzles was large; to pressurize the manifold to achieve equal flowthrough all nozzles, the flow rate of ferric chloride was higher thanplanned.

                                      TABLE 4                                     __________________________________________________________________________    PAHs in Hamilton Harbour surface                                              sediments (0-1 cm) collected in 1991                                          __________________________________________________________________________    Murphy Hamilton HARBOUR PAHs conc. ug/g Sediment Samples Summer 1991 pg.      1 of 3                                                                                        proc. blk                                                                          site 41                                                                            site 80                                                                             site 47                                                                           site 76                                                                           site 74                                                                           site 9                                                                            site 2                        __________________________________________________________________________    NAPHTHALENE     <0.01                                                                              0.61 0.24  3.86                                                                              0.11                                                                              0.15                                                                              1.14                                                                              0.15                          ACENAPHTHYLENE  ND   0.12 0.02  1.27                                                                              0.02                                                                              0.04                                                                              0.20                                                                              0.03                          ACENAPHTHENE    ND   0.05 0.02  1.53                                                                              0.03                                                                              0.04                                                                              0.25                                                                              0.06                          FLUORENE        ND   0.14 0.04  2.72                                                                              0.05                                                                              0.09                                                                              0.29                                                                              0.06                          PHENANTHRENE    <0.01                                                                              1.32 0.37  22.59                                                                             0.42                                                                              0.86                                                                              1.66                                                                              0.51                          ANTHRACENE      ND   0.20 0.03  5.01                                                                              0.07                                                                              0.18                                                                              0.41                                                                              0.08                          FLUORANTHENE    <0.01                                                                              3.38 0.86  50.36                                                                             0.85                                                                              1.86                                                                              4.33                                                                              1.02                          PYRENE          <0.01                                                                              3.01 0.76  41.07                                                                             0.74                                                                              1.61                                                                              4.04                                                                              0.88                          BENZ(a)ANTHRACENE                                                                             <0.01                                                                              1.66 0.39  33.54                                                                             0.47                                                                              0.82                                                                              2.56                                                                              0.40                          CHRYSENE        <0.01                                                                              2.16 0.56  4.36                                                                              0.61                                                                              1.05                                                                              3.00                                                                              0.62                          BENZO(B)FLUORANTHENE                                                                          <0.01                                                                              6.27 0.05  57.34                                                                             0.76                                                                              1.83                                                                              0.20                                                                              0.34                          BENZO(K)FLUORANTHENE                                                                          <0.01                                                                              0.77 0.57  41.60                                                                             0.55                                                                              0.68                                                                              3.26                                                                              0.49                          BENZO(A)PYRENE  <0.01                                                                              2.40 ND    89.29                                                                             0.31                                                                              0.23                                                                              3.75                                                                              0.15                          INDENO(1,2,3-cd)PYRENE                                                                        ND   0.51 ND    179.22                                                                            0.17                                                                              ND  0.42                                                                              0.05                          DIBENZ(a,h)ANTHRACENE                                                                         ND   0.60 ND    16.85                                                                             0.13                                                                              ND  0.40                                                                              0.02                          BENZO(ghi)PERYLENE                                                                            ND   1.05 0.07  111.47                                                                            0.31                                                                              0.05                                                                              1.42                                                                              0.13                          TOTALS          <0.01                                                                              24.25                                                                              3.98  662.10                                                                            5.60                                                                              9.48                                                                              27.35                                                                             4.98                          __________________________________________________________________________    Murphy HAMILTON HARBOUR PAHs conc. ug/g Sediment Samples Summer 1991 pg.      2 of 3                                                                                        site 25                                                                            site 15                                                                            site 45                                                                             site 9R                                                                           site 57                                                                           site 28                                                                           site 19                                                                           site 55                       __________________________________________________________________________    NAPHTHALENE     2.39 0.31 1.43  0.68                                                                              0.46                                                                              0.71                                                                              0.04                                                                              0.09                          ACENAPHTHYLENE  0.76 0.11 0.46  0.14                                                                              0.22                                                                              0.24                                                                              0.01                                                                              0.02                          ACENAPHTHENE    0.26 0.11 0.54  0.17                                                                              0.14                                                                              0.18                                                                              <0.01                                                                             0.01                          FLUORENE        0.76 0.14 0.96  0.20                                                                              0.28                                                                              0.36                                                                              0.01                                                                              0.02                          PHENANTHRENE    4.18 0.95 8.12  1.19                                                                              2.56                                                                              2.93                                                                              0.07                                                                              0.15                          ANTHRACENE      1.06 0.19 2.21  0.24                                                                              0.16                                                                              0.18                                                                              0.01                                                                              0.05                          FLUORANTHENE    17.26                                                                              2.07 11.53 3.11                                                                              4.86                                                                              5.22                                                                              0.17                                                                              0.39                          PYRENE          17.41                                                                              1.85 9.10  2.80                                                                              4.11                                                                              4.44                                                                              0.15                                                                              0.35                          BENZ(a)ANTHRACENE                                                                             15.79                                                                              1.14 4.85  1.65                                                                              2.03                                                                              2.52                                                                              0.07                                                                              0.16                          CHRYSENE        16.15                                                                              1.37 5.33  2.04                                                                              2.53                                                                              2.77                                                                              0.09                                                                              0.22                          BENZO(B)FLUORANTHENE                                                                          17.75                                                                              0.02 0.34  0.03                                                                              0.41                                                                              2.84                                                                              0.22                                                                              0.13                          BENZO(K)FLUORANTHENE                                                                          17.57                                                                              0.99 4.69  1.89                                                                              1.73                                                                              1.48                                                                              0.08                                                                              0.17                          BENZO(A)PYRENE  26.62                                                                              0.80 6.77  2.05                                                                              5.42                                                                              0.25                                                                              0.08                                                                              0.19                          INDENO(1,2,3-cd)PYRENE                                                                        6.18 0.05 0.64  0.70                                                                              0.40                                                                              ND  ND  0.01                          DIBENZ(a,h)ANTHRACENE                                                                         3.03 0.01 0.31  0.12                                                                              0.05                                                                              ND  <0.01                                                                             ND                            BENZO(ghi)PERYLENE                                                                            12.44                                                                              0.16 2.19  0.65                                                                              0.30                                                                              0.12                                                                              ND  <0.01                         TOTALS          159.60                                                                             10.26                                                                              59.47 17.67                                                                             25.64                                                                             24.26                                                                             0.98                                                                              1.96                          __________________________________________________________________________    Murphy HAMILTON HARBOUR PAHs conc. ug/g Sediment Samples Summer 1991 pg.      3 of 3                                                                                        site 36                                                                            site 28R                                                                           site 48                                                                             site 29                                                                           site 53                                                                           site 37                                                                           site 61                                                                           site 61R                      __________________________________________________________________________    NAPHTHALENE     0.83 1.00 84.82 0.41                                                                              0.36                                                                              1.17                                                                              0.65                                                                              0.84                          ACENAPHTHYLENE  0.25 0.36 2.31  0.14                                                                              0.08                                                                              0.28                                                                              0.07                                                                              0.09                          ACENAPHTHENE    0.17 0.20 14.24 0.10                                                                              0.06                                                                              0.18                                                                              0.16                                                                              0.21                          FLUORENE        0.44 0.39 21.14 0.21                                                                              0.12                                                                              0.38                                                                              0.27                                                                              0.37                          PHENANTHRENE    3.56 3.13 154.48                                                                              2.07                                                                              1.16                                                                              3.44                                                                              2.25                                                                              3.23                          ANTHRACENE      1.10 1.00 56.41 0.52                                                                              0.27                                                                              0.87                                                                              0.38                                                                              0.55                          FLUORANTHENE    6.76 5.79 167.90                                                                              3.77                                                                              2.21                                                                              6.28                                                                              3.20                                                                              4.72                          PYRENE          5.68 4.90 139.67                                                                              3.21                                                                              1.91                                                                              5.37                                                                              2.70                                                                              3.95                          BENZ(a)ANTHRACENE                                                                             3.05 3.21 90.37 1.85                                                                              0.98                                                                              3.07                                                                              1.44                                                                              2.10                          CHRYSENE        3.56 3.38 80.68 2.22                                                                              1.26                                                                              3.72                                                                              1.95                                                                              2.70                          BENZO(B)FLUORANTHENE                                                                          1.07 3.70 154.33                                                                              3.30                                                                              1.66                                                                              6.11                                                                              5.06                                                                              4.71                          BENZO(K)FLUORANTHENE                                                                          1.76 3.25 89.25 2.33                                                                              1.08                                                                              3.69                                                                              1.51                                                                              2.33                          BENZO(A)PYRENE  2.62 3.99 133.00                                                                              2.42                                                                              0.93                                                                              4.34                                                                              2.03                                                                              3.11                          INDENO(1,2,3-cd)PYRENE                                                                        ND   5.97 304.70                                                                              0.92                                                                              0.21                                                                              1.24                                                                              1.16                                                                              2.92                          DIBENZ(a,h)ANTHRACENE                                                                         ND   0.74 37.94 0.30                                                                              0.07                                                                              0.38                                                                              0.36                                                                              0.70                          BENZO(ghi)PERYLENE                                                                            0.00 2.19 135.42                                                                              1.12                                                                              0.35                                                                              1.82                                                                              1.17                                                                              2.41                          TOTALS          30.91                                                                              43.19                                                                              1,666.67                                                                            24.91                                                                             12.70                                                                             42.34                                                                             24.37                                                                             34.96                         __________________________________________________________________________

                                      TABLE 5                                     __________________________________________________________________________    PAHs in Ekman Dredge Samples - Stelco Hotspot                                               February 1990   October 1990                                                  Dredge                                                                             Dredge                                                                             Dredge                                                                              Dredge                                                                             *Core                                      Compound      Site #1                                                                            Site #2                                                                            Site #3                                                                             Site #1                                                                            Site #1                                    __________________________________________________________________________    NAPHTHALENE   2718.9                                                                             2042.1                                                                             10263.5                                                                             5457.8                                                                             2925.7                                     ACENAPHTHYLENE                                                                              13.5 19.2 16.4  8.3  14.7                                       ACENAPHTHENE  19.9 6.0  60.0  27.9 3.3                                        FLUORENE      8.6  19.0 13.3  27.1 15.5                                       PHENANTHRENE  79.6 64.7 179.0 72.8 48.5                                       ANTHRACENE    24.8 22.9 53.6  25.7 17.7                                       FLUORANTHENE  78.1 54.7 139.1 59.1 38.2                                       PYRENE        42.9 29.2 76.3  42.6 27.6                                       BENZOaANTHRACENE                                                                            41.1 24.6 59.4  20.0 12.3                                       CHRYSENE      40.3 23.1 55.0  20.1 12.5                                       BbFLUORANTHENE                                                                              42.0 21.0 58.1  14.5 7.2                                        BkFLUORANTHENE                                                                              26.4 15.7 30.1  9.5  4.9                                        BaPYRENE      38.9 20.7 49.7  12.9 6.4                                        INDENOPYRENE  24.3 13.1 30.5  8.6  4.3                                        DIBENZOANTHRACENE                                                                           4.6  3.1  5.9   2.5  1.6                                        BENZOPERYLENE 22.0 11.1 27.6  8.1  3.6                                        TOTAL (μg/g)                                                                             3225.7                                                                             2390.1                                                                             11117.6                                                                             5817.5                                                                             3143.9                                     __________________________________________________________________________     *Combined                                                                

Divers recorded with cameras that the sediments were not resuspendedinto the water column. A pressure wave proceeding the injection barraised the sediments about 20 cm, but they fell back with minimalresuspension to the upper waters. Sediment trap analysis confirms thatno sediment moved to the water surface (Table 6). A large amount of gasreached the surface and small patches of oily film formed. Somemacrophytes (primarily Elodea canadensis) were broken by the injectionbar, but most remained intact. The sediments need to be studied in moredetail but the ATP-TOX bioassay indicated a reduction in acute toxicityafter the ferric chloride treatment (FIG. 9).

On October 6, a second ferric chloride injection was done north of thefirst site to an area 200 m by 36 m. Smaller nozzles (0.031 inchdiameter orifice) were used to maintain a high back pressure in theinjection manifold and a constant flow through all the nozzles. Theskids on the injection bar were not used so that the injection bar couldpenetrate deeper into the sediments. Visual observations indicated thatthe surface 15 cm of sediments were treated. Observations that with theboom configuration, the boat could not move faster than 0.5 m/s or theinjection manifold would rise above the sediments.

EXAMPLE 2--CALCIUM NITRATE INJECTION

Calcium nitrate is about 100,000 times more water soluble than oxygen.The following reaction is mediated by bacteria:

    5CHO.sub.2 O+4NO.sub.3 .sup.-- =2N.sub.2 +4HCO.sub.3.sup.-- +CO.sub.2 +3H.sub.2 O.

Surface sediments (1-50 cm) from the St. Marys River were collected nearBellevue Park as illustrated in FIG. 6. Surface sediments (0-15 cm) werecollected from the deep basin of Hamilton Harbour as illustrated in FIG.19. Sediments were collected with either a Shipek dredge, or a Tech Opscorer. In Hamilton, samples were returned to NWRI and placed in either afridge or 12° C. incubator. In Sault Ste. Marie, samples were

                  TABLE 6                                                         ______________________________________                                        Summary of Sediment Trap Data - St. Marys River                               Chemical Treatments                                                           ______________________________________                                        Sediment Traps (g)       Sediment Traps (g)                                   July 8, 1991             Oct 10, 1991                                         Upstream                                                                              Downstream           Upstream                                                                             Downstream                                ______________________________________                                        0.122   0.182                0.066  0.049                                     0.140   0.169                0.064  0.029                                     0.154   0.144                0.047  0.074                                     0.081   0.158                0.048  0.081                                     0.497   0.653      Total     0.225  0.233                                     0.124   0.163      Average   0.056  0.058                                             +31.4      % Dif            +3.6                                      ______________________________________                                        Surface Water (g/L)      Surface Water (g/L)                                  July 8, 1991             Oct 10, 1991                                         Upstream                                                                              Downstream           Upstream                                                                             Downstream                                ______________________________________                                        0.003   0.004                0.0017 0.0015                                    ______________________________________                                    

quickly placed in a cooler and stored in a fridge in the Great LakesForestry Institute. Samples were always placed in coolers and shippedquickly. Sediment cores were subdivided within 24 h. Sediment sampleswere placed in clean pails with lids and enough sediment was added toexclude air. Sample processing for bioassays included homogenizationwith larger mixer and subsequent handling in a glove box in a fumehood.Sampling of reactors was done in a glovebox after purging it withnitrogen.

Various bottles were tried. The first trials used 300 mL BOD bottles toincubate and measure microbial utilization of nitrate. Each sample wasunique in that after opening the top, the sample was not reincubated.The microbial metabolism incubations were run using 300 mL BOD bottleswith and without 100 mg N/L of calcium nitrate. The short-termexperiments were successful, but the production of gas ruined longerincubations by popping the lids. Both 155 mL and 250 mL septum fittedbottles were used in subsequent trials for incubations with 500 mg/LN-NO₃. Biodegradation experiments were run in 155 mL glass bottles withserum caps and a 20 mL nitrogen headspace, with and without 500 mg/L Ncalcium nitrate. The nitrogen headspace was sampled with gas tightsyringes after relatively short-term incubations (2-6 weeks).

For all incubations, the sediments from the St. Marys River were mixedwith deoxygenated water from St. Marys River and the Hamilton Harboursediments were mixed with dechlorinated deoxygenated Burlington Citywater to form a 50% slurry. All the above sediments were shakencontinuously on an end-over-end shaker. In one trial to measure theproduction of ammonia, 2 L jars were used for incubations with 500 mg/LN-NO₃ ; these sediments were shaken once a day (except some weekends).

The sediment slurry was centrifuged and the supernatant was filtered andprocessed using an ion chromatograph to determine nitrate and sulphateconcentrations. The pH of samples was measured with a pH meter. Ammoniawas analyzed by colorimetric analysis (Solorzano 1969).

Volatile organic compounds in the headspace were measured by GC/MS inthe Waste Water Treatment Centre (WTC) laboratory (Brian MacGillivray).Each assay was processed with five replicate bottle incubations and theheadspace subsamples were combined. For one experiment two sets of fivereplicates were processed to determine the analytical error; it wasinsignificant. Sediment samples for hydrogen sulphide analyses werefrozen and delivered to Guelph Chemical Laboratories. These samples werepurged with helium without any pH treatment; the hydrogen sulphide wastrapped in a cold trap and injected for analysis into a GC/MS.

"Oil and grease and total petroleum hydrocarbons" was measured with aderivative of the Environment Canada (1979) protocol. "Total petroleumhydrocarbon" was measured by a gas chromatography method. Sodiumsulphate was used to dry the samples. Dichloromethane was used toextract the samples with 10 cycles/h in a Soxhlet extractor for 8 h witha water bath at 25° C.

Photobacterium bioassays were run on whole sediments (Brouwer et al.1990). Dilutions for LC₅₀ analysis were done with clean sediments fromLong Point, Lake Erie.

Results

Enhancement of Microbial Metabolism St. Marys River Sediments.

The initial laboratory reactor experiments have been successful instimulating microbial metabolism in St. Marys River sediments withcalcium nitrate. The microbial denitrification of nitrate was coupled tothe rapid production of sulphate, this is illustrated in FIGS. 20 and21. The production of sulphate reflects the microbial oxidation oforganic sulphur, hydrogen sulphide, and perhaps elemental sulphur. The100 mg/L N-NO₃ dose was completely denitrified (FIG. 20). The nextexperiment with 500 mg/L N-NO₃ resulted in incomplete denitrification ofthe added nitrate (FIG. 21). This sample was collected in late fall; thelonger lag phase in the second experiment probably indicates that themicrobes were inactive and needed more time to produce enzymes.

After two weeks of incubation, sediments treated with 500 mg/L N-NO₃were given to Dr. Reynoldson (NWRI) for bioassays. They were toxic toHexagenia. Based upon results from the second experiment (FIG. 22),these sediments had a high concentration of nitrate (>300 mg/L N-NO₃).Either the nitrate caused osmotic shock or the intense production ofnitrogen gas disrupted their intestines. This experiment needs to beredone with less calcium nitrate. There would be no similar negativeresponse in situ because no benthos would be living in sedimentsrequiring treatment. However, this experiment does illustrate the needto balance the treatment dose to the biological oxygen demand of thesediments.

In another trial using larger containers (2 L) without continuousshaking, the utilization of nitrate was slightly slower than in FIGS. 21and 22. Since these incubations used 50% slurries, these incubationsindicate that the optimal in situ does is about 350 mg/L N-NO₃. Verylittle ammonia was produced during these incubations (FIGS. 23-24).Other short-term trials indicated that phosphorus was not limitingmicrobial denitrification, that addition of iron did not suppressdenitrification, and that the pH did not decrease significantly. Forshort-term incubations, nutrients did not appear to limit microbialmetabolism and pH buffering was not required.

In one year long incubations with sediments from the St. Marys River,nitrate treatment resulted in biodegradation of about 60% of thepolynuclear aromatic hydrocarbons (PAHs, FIG. 25). The numbers in FIG.25 refer to the molecular weight of the 16 priority pollutantpolynuclear aromatic hydrocarbons. Note that the larger molecular weightcompounds that can induce tumours are biodegraded as well as the smallercompounds. This observation is inconsistent with radioisotope studiesdone in our laboratory and in other laboratories. Smaller radiolabelledPAHs can biodegrade very quickly (within weeks). As observed in theHamilton harbour studies, the conclusion is that very large PAHS thatare too large to measure with available technology are biodegrading toproduce measurable PAHs which continue to biodegrade. The rate limitingstep on the treatment is the biodegradation of the large PAHs and thetreated sites will require about two years for effective PAH treatment.

Hamilton Harbour

The rate of denitrification in a sediment sample from the deep basin ofHamilton Harbour was slightly slower than in a sample from the St. MarysRiver (Bellevue site), and much slower than in a sample from the StelcoHotspot (FIG. 26). In the sample from the deep basin of HamiltonHarbour, the denitrification resulted in the complete elimination oftoxicity to Photobacterium (FIG. 27). The incubated sample from thisStelco Hotspot had residual hydrogen sulphide and toxicity persisted.More nitrate has been added to the Stelco Hotspot incubation andanalysis will be replaced after a further six week incubation.

The oxidation of the deep basin sediments is more obvious than othersediments. These sediments were black at the start of the incubations,the control samples remained black, but the calcium nitrate treatedsamples turned brown. The sediments from the St. Marys River were not asblack, but in long incubations (three months), the control samplesturned black and the calcium nitrate samples stayed brown. The colourchange reflects the change in the oxidation state of iron.

Another simple physical change also occurs during treatments. Thecontrol samples are very flocculant and these sediments stay insuspension for days. The treated sediments are not flocculant; thesesediments precipitate within three hours after shaking. The treatmentsmust polymerize negatively charged organic colloids. This flocculationcould be very useful. Colloids can contain high concentrations ofcontaminants and their resuspension in dredging can create problems.

In general, the NWRI studies are consistent with publisheddemonstrations of biodegradation but the processes are complex and thisstudy is not complete. Simple analyses of "oil and grease" indicateabout 50% biodegradation of the organic contamination. However, "totalpetroleum hydrocarbon" analysis indicate about 90% biodegradation oforganic contamination. Some of the discrepancy is likely caused by themicrobial conversion of organic contaminants into organic compounds inliving cells.

The PAH data from headspace analysis is complex but highly encouraging.Headspace analysis of some samples indicates biodegradation of butenes,chlorobenzenes, toluene, benzene, and naphthalene at rates consistentwith other studies. Other analyses indicate production of severalcompounds, indicating cleavage of smaller molecular weight compoundsfrom larger compounds. There are about 30 analyses as complex as FIG.28. Further synthesis is required to resolve the complexities. Note thatthe analyses were replicated and the analytical error was insignificant.

The PAH analysis of the solids remaining after six weeks incubation withor without calcium nitrate indicated no significant biodegradation ofnaphthalene or other PAHs (Table 7). Analytically, the discrepancy withheadspace analysis is possible in that the headspace represents only asmall fraction of the total PAHs. The headspace is in equilibrium withfree, unbound, bioavailable compounds, but the particulate PAH analysisis done on samples extracted vigorously with dichloromethane in aSoxhlet apparatus. There are two hypotheses that can resolve the PAHdata sets. 1) Some small compounds were being cleaved from largercompounds at similar rates that

                                      TABLE 7                                     __________________________________________________________________________    PAHs in solids after chemical treatment                                       Hamilton Harbour and Sault Ste. Marie Biodegradation study Fall 1991                          Hamilton                                                                           Hamilton                                                                           Hamilton                                                                           Sault Sault Sault                                              Harbour                                                                            Harbour                                                                            Harbour                                                                            Ste. Marie                                                                          Ste. Marie                                                                          Ste. Marie                         SEDIMENT ug/g   control                                                                            FeCl3                                                                              NO3  control                                                                             FeCl3 NO3                                __________________________________________________________________________    NAPHTHALENE     0.77 0.96 0.90 4.14  2.37  4.51                               ACENAPHTHYLENE  0.19 0.27 0.23 0.26  0.18  0.23                               ACENAPTHTHENE   0.21 0.26 0.25 0.41  0.28  0.37                               FLUORENE        0.50 0.67 0.52 0.64  0.45  0.56                               PHENANTHRENE    3.36 4.59 4.24 4.45  3.09  4.00                               ANTHRACENE      0.70 1.00 1.01 1.31  0.93  1.08                               FLUORANTHENE    5.84 7.85 7.25 10.13 7.17  9.46                               PYRENE          4.05 6.70 6.24 8.44  5.97  7.90                               BENZ[a]ANTHRACENE                                                                             2.90 1.52 3.50 5.60  4.23  5.38                               CHRYSENE        4.39 5.78 5.28 7.89  5.60  7.66                               BENZO[b]FLUORANTHENE                                                                          4.92 6.05 2.77 6.38  3.76  6.68                               BENZO[k]FLUORANTHENE                                                                          4.00 4.93 4.19 5.17  3.71  5.43                               BENZO[a]PYRENE  1.00 5.60 7.43 7.02  6.45  7.30                               INDENO[1,2,3-cd]PYRENE                                                                        3.31 1.85 0.22 2.44  0.74  3.13                               DIBENZ[a,h]ANTHRACENE                                                                         1.38 1.25 0.17 1.04  0.14  1.55                               BENZO[g,h,i]PERYLENE                                                                          3.23 2.15 0.96 2.64  0.88  3.22                               TOTAL           40.75                                                                              51.43                                                                              45.16                                                                              67.94 45.95 68.47                              RETENE          0.20 0.12 0.15 24.79 18.96 23.32                              __________________________________________________________________________

microbes were biodegrading these smaller organic compounds. 2) Only asmall fraction of the PAHs are biodegradable.

Both hypotheses could be valid. Only a fraction of the total PAHs areanalyzed in the routine 16 priority PAHs, no analytical techniques existfor very large molecular weight PAHs. Also for both sites there must besome PAHs locked in coal dust or other biologically inactive matrices.The interpretation would also vary between sites. For example, theproportion of PAHs in the aqueous phase in the St. Marys Riverincubations indicates enhanced production of naphthalene from largercompounds after the treatments (Table 8). In the aqueous phase ofHamilton Harbour incubations, the treatments appear to enhancebiodegradation of naphthalene (Table 8). The uncertainties of PAHbiodegradation have been resolved with longer incubations, andincubations with ¹⁴ C-radioactively labelled naphthalene.

Pilot-scale treatments also support the laboratory incubations. Theaddition of calcium nitrate to the sediments of the Dofasco Boatslip in1992 resulted in the biodegradation of several organic compounds (meanof three samples, reductions as follows; toluene 80%, ethylbenzene 86%,m/p-xylene 76%, 3/4-ethyltoluene 89%, and dichloromethane 65%) (FIG.29). These relatively rapid biodegradation rates are similar to thosereported in laboratory studies where nitrate was added to enhancebiodegradation (Hutchins 1991).

Analysis of three samples indicates that 25% of the petroleumhydrocarbons were biodegraded in the Dofasco boatslip treatment.

The biodegradation of the PAHs (polynuclear aromatic hydrocarbons), inthe Dofasco boatslip was more complex. About 15% (450 μg/g, to 383 μg/gmean of 3 samples) of 15 PAHs were biodegraded and in the process thenaphthalene content increased 196% (280 μg/g to 549 μg/g, mean of 3samples). The imbalance in the concentration of naphthalene suggeststhat other higher

                                      TABLE 8                                     __________________________________________________________________________    PAHs in water after chemical treatments                                       Hamilton Harbour and Sault Ste. Marie Biodegradation study Fall 1991                          Hamilton                                                                           Hamilton                                                                           Hamilton                                                                           Sault Sault Sault                                              Harbour                                                                            Harbour                                                                            Harbour                                                                            Ste. Marie                                                                          Ste. Marie                                                                          Ste. Marie                                                                          Procedural                   SUPERNATANT ng/l                                                                              control                                                                            FeCl3                                                                              NO3  control                                                                             FeCl3 NO3   blank                        __________________________________________________________________________    NAPHTHALENE     410.70                                                                             205.29                                                                             43.20                                                                              178.65                                                                              2076.06                                                                             1963.06                                                                             0.04                         ACENAPHTHYLENE  145.07                                                                             79.12                                                                              8.40 20.00 35.76 33.89 nd                           ACENAPTHTHENE   247.89                                                                             71.76                                                                              nd   252.16                                                                              210.61                                                                              305.28                                                                              nd                           FLUORENE        301.13                                                                             155.29                                                                             28.00                                                                              178.11                                                                              274.55                                                                              256.39                                                                              nd                           PHENANTHRENE    1415.49                                                                            659.71                                                                             344.40                                                                             616.22                                                                              814.30                                                                              848.31                                                                              0.03                         ANTHRACENE      58.28                                                                              617.26                                                                             nd   52.43 52.91 76.11 nd                           FLUROANTHENE    790.99                                                                             365.88                                                                             434.08                                                                             635.57                                                                              719.52                                                                              854.81                                                                              0.02                         PYRENE          444.79                                                                             99.12                                                                              109.64                                                                             413.78                                                                              332.48                                                                              467.81                                                                              0.01                         BENZ[a]ANTHRACENE                                                                             45.92                                                                              16.76                                                                              22.00                                                                              78.57 45.03 85.53 0.01                         CHRYSENE        108.73                                                                             61.21                                                                              84.48                                                                              147.22                                                                              93.70 164.53                                                                              0.01                         BENZO[b]FLUORANTHENE                                                                          113.49                                                                             69.68                                                                              56.56                                                                              88.54 87.97 141.50                                                                              0.02                         BENZO[k]FLUORANTHENE                                                                          44.76                                                                              27.47                                                                              29.76                                                                              64.95 34.70 55.81 0.01                         BENZO[a]PYRENE  70.14                                                                              48.53                                                                              19.72                                                                              17.30 69.42 55.28 0.01                         INDENO[1,2,3-cd]PYRENE                                                                        44.25                                                                              nd   51.32                                                                              nd    36.52 11.81 nd                           DIBENZ[a,h]ANTHRACENE                                                                         28.68                                                                              nd   7.40 nd    11.00 nd    nd                           BENZO[g,h,i]PERYLENE                                                                          41.69                                                                              nd   22.00                                                                              nd    10.18 15.00 nd                           TOTAL           4312.00                                                                            2477.09                                                                            1260.96                                                                            2743.49                                                                             4904.70                                                                             5335.08                                                                             0.16                         RETENE          69.30                                                                              nd   0.92 582.43                                                                              267.27                                                                              85.64 0.13                         __________________________________________________________________________

molecular weight compounds not measured in the standard prioritypollutant PAH analysis are decomposing to produce naphthalene.Approximately 50% of the PAHs in coal tar pitch contain more than sevenrings (Enzminger and Ahlert 1987); we are capable of measuring less than50% of the PAHs.

At first the ability of microbes to biodegrade organic wastes seemedless probable in Hamilton Harbour sediments than in sediments from theSt. Marys River. Hamilton Harbour sediments have 10-100 times theconcentration of metals. However, the rate of headspace naphthalenebiodegradation is similar in sediments from Hamilton Harbour, St. MarysRiver, and samples from other sites (Heitkamp and Cerniglia 1987).Furthermore, the rates of denitrification in the St. Marys Riversediments, Hamilton Harbour, and other sites in Germany (Ripl 1986) aresimilar. At these sites, metals do not appear to suppress microbialbiodegradation. This is important in that many of the volatile organiccompounds that were detected in the Hamilton Harbour Hotspot (Table 9)are biodegradable.

DISCUSSION

The oxidation of toxic hydrogen sulphide eliminates most of the acutetoxicity from Hamilton Harbour and St. Marys River sediments (Murphy etal. 1992). The extreme anoxia reflected by high concentrations ofhydrogen sulphide inhibits microbial biodegradation. In headspaceanalysis, some simple compounds like butene, naphthalene, and tolueneappear to be biodegraded within weeks of nitrate addition. Thebiodegradation of larger non-volatile organic contaminants such asbenzo(a)pyrene will be slower, albeit the published rates vary greatly.Heitkamp and Cerniglia (1987) found that naphthalene, pyrene andbenzo(a)pyrene would degrade with half-lives 1.4-4.4 weeks, 38-90 weeksand 200-300 weeks, respectively. Shiaris (1989) found biodegradationturnover times of 13.2-20.1 days, 7.9-19.8 days, and 53.7-82.3 days fornaphthalene, phenanthrene, and benzo(a)pyrene, respectively. Ongoinglong-term bioassays in NWRI will help resolve the biodegradation oflarger compounds

                  TABLE 9                                                         ______________________________________                                        STELCO HOTSPOT SEDIMENT                                                       ANALYSIS BY PURGE AND TRAP GC/MS                                              PARAMETER          ng/ml                                                      ______________________________________                                        1,1-dichloroethylene                                                                             659.2                                                      dichloromethane    14.3                                                       trans-1,2-dichlorcethylene                                                                       11.3                                                       1,1-dichloroethane 97.2                                                       cis-1,2-dichloroethylene                                                                         0.0                                                        chloroform         13.0                                                       1,1,1-trichloroethane                                                                            0.0                                                        tetrachloromethane 0.0                                                        1,2-dichloroethane 18.1                                                       benzene            831.2                                                      trichloroethylene  0.0                                                        1,2-dichloropropane                                                                              0.0                                                        dibromomethane     0.0                                                        bromodichloromethane                                                                             0.0                                                        toluene            596.8                                                      1,1,2-trichloroethane                                                                            0.0                                                        tetrachloroethylene                                                                              21.6                                                       chlorodibromomethane                                                                             0.0                                                        1,2-dibromoethane  0.0                                                        chlorobenzene      0.0                                                        ethylbenzene       1348.8                                                     m/p-xylene         3002.0                                                     o-xylene           1225.2                                                     styrene            274.3                                                      cumene (isopropylbenzene)                                                                        119.3                                                      bromoform          0.0                                                        1,1,2,2-tetrachloroethane                                                                        5.9                                                        propylbenzene      112.9                                                      1,3,5-trimethylbenzene                                                                           150.8                                                      1,2,4-trimethylbenzene                                                                           14.1                                                       3-ethyltoluene     1050.0                                                     4-ethyltoluene     1247.2                                                     2-ethyltoluene     1598.0                                                     1,3-dichlorobenzene                                                                              10.3                                                       1,4-dichlorobenzene                                                                              0.0                                                        1,2-dichlorobenzene                                                                              0.0                                                        1,4-diethylbenzene 191.7                                                      1,2-diethylbenzene 9.3                                                        1,3-diethylbenzene 191.7                                                      naphthalene        35920.0                                                    hydrogen sulphide  100000.0                                                   ______________________________________                                    

like benzo(a)pyrene. The optimal study, however, would be the monitoringof pilot-scale applications of calcium nitrate to the sediments of asmany sites as possible. Each site will be slightly different and newinsights will develop from each treatment.

COMPARISON WITH FERRIC CHLORIDE TREATMENT

Because of the engineering success of the related experiments done byNWRI (Murphy et al. 1992), the calcium nitrate treatments have quicklybecome pilot-scale treatments. Both ferric chloride and calcium nitrateare oxidants. Ferric chloride is a weaker oxidant, albeit is reactionswith metals and hydrogen sulphide are more direct and potentiallyuseful. To achieve the equivalent oxidation potential of a 0.5% solutionof calcium nitrate would require that the sediments become a 10% ferricchloride solution. This latter scenario would produce a toxic low pHthat would require extensive buffering with lime. Moreover, calciumnitrate is less corrosive to equipment than ferric chloride. Thechemical cost of treating the surface 15 cm of sediments with 500 mg/LN-NO₃ would cost $2,000 to $10,000 a hectare. The range of costsreflects the chemical oxygen. The sediments of the St. Marys River anddeep basin of Hamilton Harbour require less than a third of the doserequired for the Stelco Hotspot. With the 8 m injection boom and idealconditions, about four hectares a day could be treated.

The sediments of the St. Marys River appear to be easy to treat. Theacute toxicity is caused by hydrogen sulphide and it is readily oxidizedby denitrification of added calcium nitrate (Murphy et al. 1992). Theoxidized sediments produce no toxicity to Daphnia magna, Hexagenialimbata, Escherichia coli, or Lactuca sativa. Many chlorinated compoundsoften associated with pulpmill wastes were not detected (Table 10).Benzenes are detectable in these sediments and although they arecarcinogens, they are biodegradable.

                                      TABLE 10                                    __________________________________________________________________________    CHLORINATED PHENOLS IN ST. MARYS RIVER                                        SEDIMENT CORE - JULY 8, 1991                                                  Chlorinated Phenols                                                                         SAMPLE ID (CORE DEPTH - cm)                                     (ug/kg) Dry Weight                                                                          0-1 6-7 12-14                                                                             14-16                                                                             16-18                                                                              22-24                                      __________________________________________________________________________    ortho-Chloro-phenol                                                                         *   *   *   *   *    *                                          meta-Chloro-phenol                                                                          *   *   *   *   *    *                                          para-Chloro-phenol                                                                          *   *   *   *   *    *                                          2,6-Chloro-phenol                                                                           ND  ND  ND  ND  ND   ND                                         2,4-Chloro-phenol                                                                           ND  ND  ND  ND  ND   ND                                         3,5-Chloro-phenol                                                                           ND  ND  ND  ND  ND   ND                                         2,3-Chloro-phenol                                                                           ND  ND  ND  ND  ND   ND                                         3,4-Chloro-phenol                                                                           ND  ND  ND  ND  ND   ND                                         2,4,6-Chloro-phenol                                                                         ND  ND  ND  ND  ND   ND                                         2,3,6-Chloro-phenol                                                                         ND  ND  ND  NO  ND   ND                                         2,3,5-Chloro-phenol                                                                         ND  ND  ND  ND  ND   ND                                         2,4,5-Chloro-phenol                                                                         ND  ND  ND  ND  ND   ND                                         3,4,5-Chloro-phenol                                                                         ND  ND  ND  ND  ND   ND                                         2,3,5,6-Chloro-phenol                                                                       ND  ND  ND  ND  ND   ND                                         2,3,4,5-Chloro-phenol                                                                       ND  ND  ND  ND  ND   ND                                         Penta-Chloro-phenol                                                                         ND  ND  ND  ND  ND   ND                                         4-Chloro-guaiacol                                                                           *   *   *   *   *    *                                          4,6-Chloro-guaiacol                                                                         ND  ND  ND  ND  ND   ND                                         4,5-Chloro-guaiacol                                                                         ND  ND  ND  ND  ND   ND                                         3,4,5-Chloro-guaiacol                                                                       ND  ND  ND  ND  ND   ND                                         4,5,6-Chloro-guaiacol                                                                       ND  ND  ND  ND  ND   ND                                         3,4,5,6-Chloro-guaiacol                                                                     ND  ND  ND  ND  ND   ND                                         4-Chloro-catechol                                                                           *   *   *   *   *    *                                          3,5-Chloro-catechol**                                                                       ND  ND  ND  ND  ND   ND                                         2,3,4,6-Chlorophenol**                                                        4,5-Chloro-catechol                                                                         ND  ND  ND  ND  ND   ND                                         3,4,5-Chloro-catechol                                                                       ND  ND  ND  ND  ND   ND                                         3,4,5,6-Chloro-catechol                                                                     ND  ND  ND  ND  ND   ND                                         6-Chloro-vanillin                                                                           NA  NA  NA  NA  NA   NA                                         5,6-Chloro-vanillin                                                                         ND  ND  ND  ND  ND   ND                                         Tri-chloro-syringol                                                                         ND  ND  ND  ND  ND   ND                                         4,5 Di-chloro-veratrole                                                                     ND  ND  ND  ND  ND   ND                                         3,4,5 Tri-chloro-veratrole                                                                  ND  ND  ND  ND  ND   ND                                         Tetra-chloro-veratrole                                                                      ND  ND  ND  ND  ND   ND                                         GUGICOL       *   *   *   *   *    *                                          CATECOL       *   *   *   *   *    *                                          __________________________________________________________________________     *analysis for these compounds to follow                                       **these compounds coelute                                                     ND not detected                                                               NA not applicable                                                        

The concentration of PAHs is relatively low (Table 3; Murphy et al. 192,Table 1). The concentration of PAHs is approximately at the apparenteffects threshold--the concentration where you begin to see toxiceffects on the ecosystem (Long and Morgan 1990). There is no evidencethat the PAHs in the sediments at the Bellevue site are a problem.Chemical data, particularly threshold concentrations, must be usedcautiously. The high concentration of organic matter found in thesediments of the St. Marys River could reduce the bioavailability ofPAHs as has been found at other sites (Landrum et al. 1987). As well asconducting additional chemical analyses, the endpoint of thebiodegradation should be determined with bioassays. The best bioassaywould be the response of the benthos in treated sediments.

We claim:
 1. An apparatus for treating sediment in a water body, saidsediment containing chemical pollutants, comprising:a main supportmember; a first dispensing means, mounted in spaced relation to saidmain support member, adapted for dispensing a treatment compound intothe sediment to be treated at a first level; a second dispensing meansadapted for dispensing said treatment compound into said sediment at asecond level, said second dispensing means comprising a plurality ofindividual flexible hoses, each having a nozzle at one end and connectedat an opposed end to said first dispensing means for reception of saidtreatment compound; resilient support means for supporting of saidsecond dispensing means, said resilient support means adapted forpenetrating said sediment, said resilient support means comprising aplurality of flexible fingers mounted to said main support member andseparate from said first dispensing means and said second dispensingmeans; and means for connection for said first dispensing means with asupply of said treatment compound.
 2. The apparatus as claimed in claim1, wherein said apparatus further includes mounting means for mountingsaid apparatus to a carrier vessel.
 3. The apparatus as claimed in claim2, wherein said fingers each comprise a sinusoidally shaped member. 4.The apparatus as claimed in claim 3, wherein each of said fingersincludes one end connected at a single point to said main support memberand a free end.
 5. The apparatus as claimed in claim 4, wherein saidfingers are in a longitudinally aligned and spaced relationship.
 6. Anapparatus for treating sediment in a water body, said sedimentcontaining chemical pollutants, comprising, in combination:a mainsupport member; a first dispensing means mounted in spaced relation tosaid main support member, said first dispensing means adapted fordispensing a treatment compound into the sediment to be treated at afirst level; a second dispensing means adapted for dispensing saidtreatment compound into said sediment at a second level, said seconddispensing means comprising a plurality of individual flexible hoses,each having a nozzle at one end and connected at an opposed end to saidfirst dispensing means for reception of said treatment compound; saidfirst dispensing means having means for connection with a supply of saidtreatment compound; resilient support means for supporting said seconddispensing means and for penetrating said sediment, said resilient meanscomprising a plurality of arcuately-shaped flexible fingers mounted tosaid main support member and separate from said first dispensing meansand said second dispensing means; mounting means for mounting saidapparatus to a carrier vessel; and a carrier vessel for mounting saidapparatus.
 7. The apparatus as claimed in claim 6, wherein said carriervessel includes a rotatable platform connected to said mounting meansfor permitting rotation of said apparatus.
 8. The apparatus as claimedin claim 6, wherein said flexible fingers comprise flexible metal bars.9. The apparatus as claimed in claim 6, wherein each of said flexiblefingers includes an end connected to said main support member and anopposed free end.
 10. The apparatus as claimed in claim 9, wherein saidnozzle is spaced from said free end of each finger.